Processes comprising crosslinking polyethylene or using crosslinked polyethylene

Abstract

Provided are processes comprising crosslinking polyethylene or using crosslinked polyethylene. Furthermore, the processes may include compacting and/or sintering the polyethylene. The polyethylene can comprise virgin ultrahigh molecular weight polyethylene having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin ultrahigh molecular weight polyethylene.

What is claimed is: 
     
       1. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said compacting occurs at a temperature in the range of 60-135° C.; and 
 wherein said compacting is performed under shear. 
 
     
     
       2. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said crosslinking is initiated before said sintering. 
 
     
     
       3. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said crosslinking is initiated during said sintering. 
 
     
     
       4. The process according to  claim 1 , wherein said crosslinking is initiated after said sintering. 
     
     
       5. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said compacting occurs in an inert atmosphere. 
 
     
     
       6. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said compacting occurs in a reactive atmosphere. 
 
     
     
       7. A process comprising:
 providing a compacted composition, said compacted composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol; 
 crosslinking the UHMWPE; 
 sintering the composition; and 
 cooling the sintered compacted polyethylene at a rate of less than 10° C/hr. 
 
     
     
       8. The process of  claim 7 , wherein said UHMW PE has a weight average molecular weight of at least 2,000,000 g/mol. 
     
     
       9. The process according to  claim 7 , wherein said sintering occurs in an inert atmosphere. 
     
     
       10. The process according to  claim 7 , wherein said sintering occurs in a reactive atmosphere. 
     
     
       11. The process according to  claim 7 , wherein said crosslinking is initiated before said sintering. 
     
     
       12. The process according to  claim 7 , wherein said crosslinking is initiated during said sintering. 
     
     
       13. The process according to  claim 7 , wherein said crosslinking is initiated during said cooling. 
     
     
       14. A process comprising:
 providing a compacted composition, said compacted composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol; 
 crosslinking the UHMWPE; 
 sintering the composition; and 
 cooling the sintered compacted polyethylene; and 
 wherein said cooling is temporarily stopped at a temperature about 1-10° C. above the crystallization temperature of said UHMW PE. 
 
     
     
       15. The process according to  claim 7 , wherein said polyethylene is medical grade polyethylene. 
     
     
       16. The process according to  claim 7 , wherein said composition consists essentially of said UHMW PE. 
     
     
       17. The process according to  claim 7 , wherein said composition comprises a linear polyethylene having a weight average molecular weight below 500,000 g/mol. 
     
     
       18. The process according to  claim 7 , wherein said composition comprises a polyethylene having a weight average molecular weight below 25,000 g/mol. 
     
     
       19. The process according to  claim 7 , wherein said compacted composition has the shape of a block. 
     
     
       20. The process according to  claim 7 , wherein said process is absent melting the UHMW PE other than during said sintering. 
     
     
       21. The process according to  claim 7 , further comprising machining the crosslinked composition into a part of an orthopedic implant. 
     
     
       22. The process of  claim 21 , wherein said orthopedic implant is a hip cup or a part of an artificial knee. 
     
     
       23. An article obtained by the process according to  claim 7 . 
     
     
       24. An orthopedic implant comprising the article of  claim 23 . 
     
     
       25. The process of  claim 7 , wherein said composition comprises, relative to the total weight of said composition, at least 75 wt % of said UHMW PE. 
     
     
       26. A process comprising:
 sintering ultrahigh molecular weight polyethylene (UHMW PE); 
 initiating a first crosslinking of said UHMW PE during said sintering; 
 cooling the sintered UHMW PE; and 
 initiating a second crosslinking of said UHMW PE during said cooling. 
 
     
     
       27. The process of  claim 26 , wherein said crosslinking is effected with radiation, and the dose used during said sintering is smaller than the dose used during said cooling. 
     
     
       28. A process comprising:
 compacting a composition comprising virgin ultrahigh molecular weight polyethylene (UHMW PE), said UHMW PE having a weight average molecular weight of at least 1,000,000 g/mol, to provide a compacted composition comprising virgin UHMW PE; 
 sintering said compacted composition; and 
 crosslinking said UHMW PE; and 
 wherein said compacting is performed under shear. 
 
     
     
       29. The process according to  claim 5 , wherein said crosslinking is initiated after said sintering.